BMP1-like proteinases are essential to the structure and wound healing of skin

Transcriptional profiling of lung macrophages following ozone exposure in mice identifies signaling pathways regulating immunometabolic activation

Macrophages play a key role in ozone-induced lung injury by regulating both the initiation and resolution of inflammation. These distinct activities are mediated by pro-inflammatory and anti-inflammatory/proresolution macrophages which sequentially accumulate in injured tissues. Macrophage activation is dependent, in part, on intracellular metabolism. Herein, we used RNA-sequencing (seq) to identify signaling pathways regulating macrophage immunometabolic activity following exposure of mice to ozone (0.8 ppm, 3 h) or air control. Analysis of lung macrophages using an Agilent Seahorse showed that inhalation of ozone increased macrophage glycolytic activity and oxidative phosphorylation at 24 and 72 h post-exposure. An increase in the percentage of macrophages in S phase of the cell cycle was observed 24 h post ozone. RNA-seq revealed significant enrichment of pathways involved in innate immune signaling and cytokine production among differentially expressed genes at both 24 and 72 h after ozone, whereas pathways involved in cell cycle regulation were upregulated at 24 h and intracellular metabolism at 72 h. An interaction network analysis identified tumor suppressor 53 (TP53), E2F family of transcription factors (E2Fs), cyclin-dependent kinase inhibitor 1A (CDKN1a/p21), and cyclin D1 (CCND1) as upstream regulators of cell cycle pathways at 24 h and TP53, nuclear receptor subfamily 4 group a member 1 (NR4A1/Nur77), and estrogen receptor alpha (ESR1/ERα) as central upstream regulators of mitochondrial respiration pathways at 72 h. To assess whether ERα regulates metabolic activity, we used ERα-/- mice. In both air and ozone-exposed mice, loss of ERα resulted in increases in glycolytic capacity and glycolytic reserve in lung macrophages with no effect on mitochondrial oxidative phosphorylation. Taken together, these results highlight the complex interaction between cell cycle, intracellular metabolism, and macrophage activation which may be important in the initiation and resolution of inflammation following ozone exposure.

A new method for network bioinformatics identifies novel drug targets for mucinous ovarian carcinoma

Mucinous ovarian carcinoma (MOC) is a subtype of ovarian cancer that is distinct from all other ovarian cancer subtypes and currently has no targeted therapies. To identify novel therapeutic targets, we developed and applied a new method of differential network analysis comparing MOC to benign mucinous tumours (in the absence of a known normal tissue of origin). This method mapped the protein-protein network in MOC and then utilised structural bioinformatics to prioritise the proteins identified as upregulated in the MOC network for their likelihood of being successfully drugged. Using this protein-protein interaction modelling, we identified the strongest 5 candidates, CDK1, CDC20, PRC1, CCNA2 and TRIP13, as structurally tractable to therapeutic targeting by small molecules. siRNA knockdown of these candidates performed in MOC and control normal fibroblast cell lines identified CDK1, CCNA2, PRC1 and CDC20, as potential drug targets in MOC. Three targets (TRIP13, CDC20, CDK1) were validated using known small molecule inhibitors. Our findings demonstrate the utility of our pipeline for identifying new targets and highlight potential new therapeutic options for MOC patients.

Mono- and Bi-specific Nanobodies Targeting the CUB Domains of PCPE-1 Reduce the Proteolytic Processing of Fibrillar Procollagens

The excessive deposition of fibrillar collagens is a hallmark of fibrosis. Collagen fibril formation requires proteolytic maturations by Procollagen N- and C-proteinases (PNPs and PCPs) to remove the N- and C-propeptides which maintain procollagens in the soluble form. Procollagen C-Proteinase Enhancer-1 (PCPE-1, a glycoprotein composed of two CUB domains and one NTR domain) is a regulatory protein that activates the C-terminal processing of procollagens by the main PCPs. It is often up-regulated in fibrotic diseases and represents a promising target for the development of novel anti-fibrotic strategies. Here, our objective was to develop the first antagonists of PCPE-1, based on the nanobody scaffold. Using both an in vivo selection through the immunization of a llama and an in vitro selection with a synthetic library, we generated 18 nanobodies directed against the CUB domains of PCPE1, which carry its enhancing activity. Among them, I5 from the immune library and H4 from the synthetic library have a high affinity for PCPE-1 and inhibit its interaction with procollagens. The crystal structure of the complex formed by PCPE-1, H4 and I5 showed that they have distinct epitopes and enabled the design of a biparatopic fusion, the diabody diab-D1. Diab-D1 has a sub-nanomolar affinity for PCPE-1 and is a potent antagonist of its activity, preventing the stimulation of procollagen cleavage in vitro. Moreover, Diab-D1 is also effective in reducing the proteolytic maturation of procollagen I in cultures of human dermal fibroblasts and hence holds great promise as a tool to modulate collagen deposition in fibrotic conditions.

Convergent and divergent transcriptional reprogramming of motor and sensory neurons underlying response to peripheral nerve injury

INTRODUCTION

Motor neurons differ from sensory neurons in aspects including origins and surrounding environment. Understanding the similarities and differences in molecular response to peripheral nerve injury (PNI) and regeneration between sensory and motor neurons is crucial for developing effective drug targets for CNS regeneration. However, genome-wide comparisons of molecular changes between sensory and motor neurons following PNI remains limited.

OBJECTIVES

This study aims to investigate genome-wide convergence and divergence of injury response between sensory and motor neurons to identify novel drug targets for neural repair.

METHODS

We analyzed two large-scale RNA-seq datasets of in situ captured sensory neurons (SNs) and motoneurons (MNs) upon PNI, retinal ganglion cells and spinal cord upon CNS injury. Additionally, we integrated these with other related single-cell level datasets. Bootstrap DESeq2 and WGCNA were used to detect and explore co-expression modules of differentially expressed genes (DEGs).

RESULTS

We found that SNs and MNs exhibited similar injury states, but with a delayed response in MNs. We identified a conserved regeneration-associated module (cRAM) with 274 shared DEGs. Of which, 47% of DEGs could be changed in injured neurons supported by single-cell resolution datasets. We also identified some less-studied candidates in cRAM, including genes associated with transcription, ubiquitination (Rnf122), and neuron-immune cells cross-talk. Further in vitro experiments confirmed a novel role of Rnf122 in axon growth. Analysis of the top 10% of DEGs with a large divergence suggested that both extrinsic (e.g., immune microenvironment) and intrinsic factors (e.g., development) contributed to expression divergence between SNs and MNs following injury.

CONCLUSIONS

This comprehensive analysis revealed convergent and divergent injury response genes in SNs and MNs, providing new insights into transcriptional reprogramming of sensory and motor neurons responding to axonal injury and subsequent regeneration. It also identified some novel regeneration-associated candidates that may facilitate the development of strategies for axon regeneration.

Epidermal or Dermal Collagen VII Is Sufficient for Skin Integrity: Insights to Anchoring Fibril Homeostasis

Collagen VII forms anchoring fibrils that are essential for the stability of the skin and other epithelial organs. In addition to such structural functions, it is emerging that collagen VII fills instructive functions. Collagen VII is synthesized by both epithelial cells and fibroblasts. Genetic loss of collagen VII causes dystrophic epidermolysis bullosa, which manifests with chronic skin fragility and fibrosis. Significant progress has been made in developing therapies for dystrophic epidermolysis bullosa; however, such work has also raised questions on the importance of the cellular source of collagen VII for maintenance of tissue integrity and homeostasis. Toward this end, we engineered mice that kept the physiological expression of collagen VII only in epithelial cells or in fibroblasts. Our study revealed that production of collagen VII either by keratinocytes or fibroblasts alone is sufficient for creation of mechanically robust skin. Importantly, we also show tissue-diverse dependence on epithelial and mesenchymal production of collagen VII and provide support for limited amounts of collagen VII being sufficient for tissue protection. Furthermore, a disconnect between collagen VII abundance and anchoring fibril numbers supports the concept that restoration of fully physiological collagen VII levels may not be needed to achieve complete mechanical protection of dystrophic epidermolysis bullosa skin.

Antiviral drugs prolong survival in murine recessive dystrophic epidermolysis bullosa

Recessive dystrophic epidermolysis bullosa (RDEB) is a rare inherited skin disease characterized by defects in type VII collagen leading to a range of fibrotic pathologies resulting from skin fragility, aberrant wound healing, and altered dermal fibroblast physiology. Using a novel in vitro model of fibrosis based on endogenously produced extracellular matrix, we screened an FDA-approved compound library and identified antivirals as a class of drug not previously associated with anti-fibrotic action. Preclinical validation of our lead hit, daclatasvir, in a mouse model of RDEB demonstrated significant improvement in fibrosis as well as overall quality of life with increased survival, weight gain and activity, and a decrease in pruritus-induced hair loss. Immunohistochemical assessment of daclatasvir-treated RDEB mouse skin showed a reduction in fibrotic markers, which was supported by in vitro data demonstrating TGFβ pathway targeting and a reduction of total collagen retained in the extracellular matrix. Our data support the clinical development of antivirals for the treatment of patients with RDEB and potentially other fibrotic diseases.

Genome-wide identification and structural analysis of the BMP gene family in Triplophysa dalaica

BACKGROUND

Bone morphogenetic proteins (BMPs) are part of the transforming growth factor beta (TGF-β) superfamily and play crucial roles in bone development, as well as in the formation and maintenance of various organs. Triplophysa dalaica, a small loach fish that primarily inhabits relatively high elevations and cooler water bodies, was the focus of this study. Understanding the function of BMP genes during the morphogenesis of T. dalaica helps to clarify the mechanisms of its evolution and serves as a reference for the study of BMP genes in other bony fishes. The data for the T. dalaica transcriptome and genome used in this investigation were derived from the outcomes of our laboratory sequencing.

RESULTS

This study identified a total of 26 BMP genes, all of which, except for BMP1, possess similar TGF-β structural domains. We conducted an analysis of these 26 BMP genes, examining their physicochemical properties, subcellular localization, phylogenetic relationships, covariance within and among species, chromosomal localization, gene structure, conserved motifs, conserved structural domains, and expression patterns. Our findings indicated that three BMP genes were associated with unstable proteins, while 11 BMP genes were located within the extracellular matrix. Furthermore, some BMP genes were duplicated, with the majority being enriched in the GO:0008083 pathway, which is related to growth factor activity. It was hypothesized that genes within the BMP1/3/11/15 subgroup (Group I) play a significant role in the growth and development of T. dalaica. By analyzing the expression patterns of proteins in nine tissues (gonad, kidney, gill, spleen, brain, liver, fin, heart, and muscle), we found that BMP genes play diverse regulatory roles during different stages of growth and development and exhibit characteristics of division of labor.

CONCLUSIONS

This study contributes to a deeper understanding of BMP gene family member expression patterns in high-altitude, high-salinity environments and provides valuable insights for future research on the BMP gene family in bony fishes.

Identification of PCPE-2 as the endogenous specific inhibitor of human BMP-1/tolloid-like proteinases

BMP-1/tolloid-like proteinases (BTPs) are major players in tissue morphogenesis, growth and repair. They act by promoting the deposition of structural extracellular matrix proteins and by controlling the activity of matricellular proteins and TGF-β superfamily growth factors. They have also been implicated in several pathological conditions such as fibrosis, cancer, metabolic disorders and bone diseases. Despite this broad range of pathophysiological functions, the putative existence of a specific endogenous inhibitor capable of controlling their activities could never be confirmed. Here, we show that procollagen C-proteinase enhancer-2 (PCPE-2), a protein previously reported to bind fibrillar collagens and to promote their BTP-dependent maturation, is primarily a potent and specific inhibitor of BTPs which can counteract their proteolytic activities through direct binding. PCPE-2 therefore differs from the cognate PCPE-1 protein and extends the possibilities to fine-tune BTP activities, both in physiological conditions and in therapeutic settings.

Mechanotransduction through hemidesmosomes during aging and longevity

Hemidesmosomes are structural protein complexes localized at the interface of tissues with high mechanical demand and shear forces. Beyond tissue anchoring, hemidesmosomes have emerged as force-modulating structures important for translating mechanical cues into biochemical and transcriptional adaptation (i.e. mechanotransduction) across tissues. Here, we discuss the recent insights into the roles of hemidesmosomes in age-related tissue regeneration and aging in C. elegans, mice and humans. We highlight the emerging concept of preserved dynamic mechanoregulation of hemidesmosomes in tissue maintenance and healthy aging.

Evaluation in a porcine wound model and long-term clinical assessment of an autologous heterogeneous skin construct used to close full-thickness wounds

Acute and chronic wounds involving deeper layers of the skin are often not adequately healed by dressings alone and require therapies such as skin grafting, skin substitutes, or growth factors. Here we report the development of an autologous heterogeneous skin construct (AHSC) that aids wound closure. AHSC is manufactured from a piece of healthy full-thickness skin. The manufacturing process creates multicellular segments, which contain endogenous skin cell populations present within hair follicles. These segments are physically optimized for engraftment within the wound bed. The ability of AHSC to facilitate closure of full thickness wounds of the skin was evaluated in a swine model and clinically in 4 patients with wounds of different etiologies. Transcriptional analysis demonstrated high concordance of gene expression between AHSC and native tissues for extracellular matrix and stem cell gene expression panels. Swine wounds demonstrated complete wound epithelialization and mature stable skin by 4 months, with hair follicle development in AHSC-treated wounds evident by 15 weeks. Biomechanical, histomorphological, and compositional analysis of the resultant swine and human skin wound biopsies demonstrated the presence of epidermal and dermal architecture with follicular and glandular structures that are similar to native skin. These data suggest that treatment with AHSC can facilitate wound closure.

The Extracellular Matrix: Its Composition, Function, Remodeling, and Role in Tumorigenesis

The extracellular matrix (ECM) is a ubiquitous member of the body and is key to the maintenance of tissue and organ integrity. Initially thought to be a bystander in many cellular processes, the extracellular matrix has been shown to have diverse components that regulate and activate many cellular processes and ultimately influence cell phenotype. Importantly, the ECM's composition, architecture, and stiffness/elasticity influence cellular phenotypes. Under normal conditions and during development, the synthesized ECM constantly undergoes degradation and remodeling processes via the action of matrix proteases that maintain tissue homeostasis. In many pathological conditions including fibrosis and cancer, ECM synthesis, remodeling, and degradation is dysregulated, causing its integrity to be altered. Both physical and chemical cues from the ECM are sensed via receptors including integrins and play key roles in driving cellular proliferation and differentiation and in the progression of various diseases such as cancers. Advances in 'omics' technologies have seen an increase in studies focusing on bidirectional cell-matrix interactions, and here, we highlight the emerging knowledge on the role played by the ECM during normal development and in pathological conditions. This review summarizes current ECM-targeted therapies that can modify ECM tumors to overcome drug resistance and better cancer treatment.

A combined analysis of bulk and single-cell sequencing data reveals that depleted extracellular matrix and enhanced immune processes co-contribute to fluorouracil beneficial responses in gastric cancer

Fluorouracil, also known as 5-FU, is one of the most commonly used chemotherapy drugs in the treatment of advanced gastric cancer (GC). Whereas, the presence of innate or acquired resistance largely limits its survival benefit in GC patients. Although accumulated studies have demonstrated the involvement of tumor microenvironments (TMEs) in chemo-resistance induction, so far little is known about the relevance of GC TMEs in 5-FU resistance. To this end, in this study, we investigated the relationship between TME features and 5-FU responses in GC patients using a combined analysis involving both bulk sequencing data from the TCGA database and single-cell RNA sequencing data from the GEO database. We found that depleted extracellular matrix (ECM) components such as capillary/stroma cells and enhanced immune processes such as increased number of M1 polarized macrophages/Memory T cells/Natural Killer T cells/B cells and decreased number of regulatory T cells are two important features relating to 5-FU beneficial responses in GC patients, especially in diffuse-type patients. We further validated these two features in the tumor tissues of 5-FU-benefit GC patients using immunofluorescence staining experiments. Based on this finding, we also established a Pro (63 genes) and Con (199 genes) gene cohort that could predict 5-FU responses in GC with an AUC (area under curve) score of 0.90 in diffuse-type GC patients, and further proved the partial applicability of this gene panel pan-cancer-wide. Moreover, we identified possible communications mediated by heparanase and galectin-1 which could regulate ECM remodeling and tumor immune microenvironment (TIME) reshaping. Altogether, these findings deciphered the relationship between GC TMEs and 5-FU resistance for the first time, as well as provided potential therapeutic targets and predicting rationale to overcome this chemo-resistance, which could shed some light on developing novel precision treatment strategies in clinical practice.

Deficiency of Procollagen C-Proteinase Enhancer 1 in Mice has No Major Impact on Cardiac Collagen and Function Under Basal Conditions

ABSTRACT

Maturation of fibrillar collagen is known to play a crucial role in the pathophysiology of myocardial fibrosis. Procollagen C-proteinase enhancer 1 (PCPE1) has a key role in procollagen maturation and collagen fibril formation. The phenotype of both male and female PCPE1 knock-out mice was investigated under basal conditions to explore the potential of PCPE1 as a therapeutic target in heart failure. Global constitutive PCPE1-/- mice were generated. Serum procollagen I C-terminal propeptide, organ histology, and cutaneous wound healing were assessed in both wild type (WT) and PCPE1-/- mice. In addition, the cardiac expression of genes involved in collagen metabolism was investigated and the total and insoluble cardiac collagen contents determined. Cardiac function was evaluated by echocardiography. No differences in survival, clinical chemistry, or organ histology were observed in PCPE1-/- mice compared with WT. Serum procollagen I C-terminal propeptide was lower in PCPE1-/- mice. Cardiac mRNA expression of Bmp1, Col1a1, Col3a1, and Loxl2 was similar, whereas Tgfb and Loxl1 mRNA levels were decreased in PCPE1-/- mice compared with sex-matched WT. No modification of total or insoluble cardiac collagen content was observed between the 2 strains. Ejection fraction was slightly decreased in PCPE1-/- male mice, but not in females. Finally, wound healing was not altered in PCPE1-/- mice. PCPE1 deficiency does not trigger any major liabilities and does not affect cardiac collagen content nor its function under basal conditions. Further studies are required to evaluate its role under stressed conditions and determine its suitability as a therapeutic target for heart failure.

Distinct contributions of meprins to skin regeneration after injury - Meprin α a physiological processer of pro-collagen VII

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Meprins subtly support epidermal and dermal skin wound healing.

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Loss of both meprins reduces re-epithelialization and wound macrophage abundance.

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Meprin α is a physiological maturing proteinase of collagen VII.

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Meprins are reduced in recessive dystrophic epidermolysis bullosa skin.

Astacin-like proteinases (ALPs) are regulators of tissue and extracellular matrix (ECM) homeostasis. They convey this property through their ability to convert ECM protein pro-forms to functional mature proteins and by regulating the bioavailability of growth factors that stimulate ECM synthesis. The most studied ALPs in this context are the BMP-1/tolloid-like proteinases. The other subclass of ALPs in vertebrates – the meprins, comprised of meprin α and meprin β – are emerging as regulators of tissue and ECM homeostasis but have so far been only limitedly investigated. Here, we functionally assessed the roles of meprins in skin wound healing using mice genetically deficient in one or both meprins. Meprin deficiency did not change the course of macroscopic wound closure. However, subtle but distinct contributions of meprins to the healing process and dermal homeostasis were observed. Loss of both meprins delayed re-epithelialization and reduced macrophage infiltration. Abnormal dermal healing and ECM regeneration was observed in meprin deficient wounds. Our analyses also revealed meprin α as one proteinase responsible for maturation of pro-collagen VII to anchoring fibril-forming-competent collagen VII in vivo. Collectively, our study identifies meprins as subtle players in skin wound healing.

Procollagen C-proteinase enhancer-1 (PCPE-1), a potential biomarker and therapeutic target for fibrosis

The correct balance between collagen synthesis and degradation is essential for almost every aspect of life, from development to healthy aging, reproduction and wound healing. When this balance is compromised by external or internal stress signals, it very often leads to disease as is the case in fibrotic conditions. Fibrosis occurs in the context of defective tissue repair and is characterized by the excessive, aberrant and debilitating deposition of fibril-forming collagens. Therefore, the numerous proteins involved in the biosynthesis of fibrillar collagens represent a potential and still underexploited source of therapeutic targets to prevent fibrosis. One such target is procollagen C-proteinase enhancer-1 (PCPE-1) which has the unique ability to accelerate procollagen maturation by BMP-1/tolloid-like proteinases (BTPs) and contributes to trigger collagen fibrillogenesis, without interfering with other BTP functions or the activities of other extracellular metalloproteinases. This role is achieved through a fine-tuned mechanism of action that is close to being elucidated and offers promising perspectives for drug design. Finally, the in vivo data accumulated in recent years also confirm that PCPE-1 overexpression is a general feature and early marker of fibrosis. In this review, we describe the results which presently support the driving role of PCPE-1 in fibrosis and discuss the questions that remain to be solved to validate its use as a biomarker or therapeutic target.

Effects of bone morphogenetic proteins on epithelial repair

Epithelial tissue has important functions such as protection, secretion, and sensation. Epithelial damage is involved in various pathological processes. Bone morphogenetic proteins (BMPs) are a class of growth factors with multiple functions. They play important roles in epithelial cells, including in differentiation, proliferation, and migration during the repair of the epithelium. This article reviews the functions and mechanisms of the most profoundly studied BMPs in the process of epithelial damage repair and their clinical significance.

Characterization of tolloid-mediated cleavage of the GDF8 procomplex

Growth differentiation factor 8 (GDF8), a.k.a. myostatin, is a member of the larger TGFβ superfamily of signaling ligands. GDF8 has been well characterized as a negative regulator of muscle mass. After synthesis, GDF8 is held latent by a noncovalent complex between the N-terminal prodomain and the signaling ligand. Activation of latent GDF8 requires proteolytic cleavage of the prodomain at residue D99 by a member of the tolloid family of metalloproteases. While tolloid proteases cleave multiple substrates, they lack a conserved consensus sequence. Here, we investigate the tolloid cleavage site of the GDF8 prodomain to determine what residues contribute to tolloid recognition and subsequent proteolysis. Using sequential alanine mutations, we identified several residues adjacent to the scissile bond, including Y94, that when mutated, abolish tolloid-mediated activation of latent GDF8. Using the astacin domain of Tll1 (Tolloid Like 1) we determined that prodomain mutants were more resistant to proteolysis. Purified latent complexes harboring the prodomain mutations, D92A and Y94A, impeded activation by tolloid but could be fully activated under acidic conditions. Finally, we show that co-expression of GDF8 WT with prodomain mutants that were tolloid resistant, suppressed GDF8 activity. Taken together our data demonstrate that residues towards the N-terminus of the scissile bond are important for tolloid-mediated activation of GDF8 and that the tolloid-resistant version of the GDF8 prodomain can function dominant negative to WT GDF8.

Proteinase bone morphogenetic protein 1, but not tolloid-like 1, plays a dominant role in maintaining periodontal homeostasis

BACKGROUND

Periodontitis is caused by multiple factors involving a bacterial challenge and a susceptible host, although there is no report on gene mutation directly linked to this common disease. Mutations in the proteinase bone morphogenetic protein 1 (BMP1) were identified in patients with osteogenesis imperfecta, who display some dentin defects and alveolar bone loss. We previously reported essential roles of BMP1 and tolloid-like 1 (TLL1), two closely related extracellular proteinases with overlapping functions, in mouse periodontium growth by simultaneous knockout (KO) of both genes, although the separate roles of BMP1 and TLL1 have remained unclear. Here, we have investigated whether and how BMP1 and TLL1 separately maintain periodontal homeostasis by comparing single Bmp1 KO and Tll1 KO with double KO (dKO) phenotypes.

METHODS

Floxed Bmp1 and/or Tll1 alleles were deleted in transgenic mice via ubiquitously expressed Cre^ERT2 induced by tamoxifen treatment starting at 4-weeks of age (harvested at 18-weeks of age). Multiple approaches, including X-ray, micro-CT, calcein and alizarin red double-labeling, scanning electron microscopy, and histological and immunostaining assays, were used to analyze periodontal phenotypes and molecular mechanisms.

RESULTS

Both Bmp1 KO and double KO mice exhibited severe periodontal defects, characterized by periodontal ligament (PDL) fiber loss and ectopic ossification in the expanded PDL area, and drastic reductions in alveolar bone and cementum volumes, whereas Tll1 KO mice displayed very mild phenotypes. Mechanistic studies revealed a sharp increase in the uncleaved precursor of type I collagen (procollagen I), leading to defective extracellular matrices.

CONCLUSIONS

BMP1, but not TLL1, is essential for maintaining periodontal homeostasis. This occurs at least partly via biosynthetic processing of procollagen I, thereby maintaining appropriate levels of procollagen I and its activated products such as mature collagen I.

BMP-1 disrupts cell adhesion and enhances TGF-β activation through cleavage of the matricellular protein thrombospondin-1

Bone morphogenetic protein 1 (BMP-1) is an important metalloproteinase that synchronizes growth factor activation with extracellular matrix assembly during morphogenesis and tissue repair. The mechanisms by which BMP-1 exerts these effects are highly context dependent. Because BMP-1 overexpression induces marked phenotypic changes in two human cell lines (HT1080 and 293-EBNA cells), we investigated how BMP-1 simultaneously affects cell-matrix interactions and growth factor activity in these cells. Increasing BMP-1 led to a loss of cell adhesion that depended on the matricellular glycoprotein thrombospondin-1 (TSP-1). BMP-1 cleaved TSP-1 between the VWFC/procollagen-like domain and the type 1 repeats that mediate several key TSP-1 functions. This cleavage induced the release of TSP-1 C-terminal domains from the extracellular matrix and abolished its previously described multisite cooperative interactions with heparan sulfate proteoglycans and CD36 on HT1080 cells. In addition, BMP-1-dependent proteolysis potentiated the TSP-1-mediated activation of latent transforming growth factor-β (TGF-β), leading to increased signaling through the canonical SMAD pathway. In primary human corneal stromal cells (keratocytes), endogenous BMP-1 cleaved TSP-1, and the addition of exogenous BMP-1 enhanced cleavage, but this had no substantial effect on cell adhesion. Instead, processed TSP-1 promoted the differentiation of keratocytes into myofibroblasts and stimulated production of the myofibroblast marker α-SMA, consistent with the presence of processed TSP-1 in human corneal scars. Our results indicate that BMP-1 can both trigger the disruption of cell adhesion and stimulate TGF-β signaling in TSP-1-rich microenvironments, which has important potential consequences for wound healing and tumor progression.

Skin proteomics - analysis of the extracellular matrix in health and disease

INTRODUCTION

The skin protects the human body from external insults and regulates water and temperature homeostasis. A highly developed extracellular matrix (ECM) supports the skin and instructs its cell functions. Reduced functionality of the ECM is often associated with skin diseases that cause physical impairment and also have implications on social interactions and quality of life of affected individuals.

AREAS COVERED

With a focus on the skin ECM we discuss how mass spectrometry (MS)-based proteomic approaches first contributed to establishing skin protein inventories and then facilitated elucidation of molecular functions and disease mechanisms.

EXPERT OPINION

MS-based proteomic approaches have significantly contributed to our understanding of skin pathophysiology, but also revealed the challenges in assessing the skin ECM. The numerous posttranslational modifications of ECM proteins, like glycosylation, crosslinking, oxidation, and proteolytic maturation in disease settings can be difficult to tackle and remain understudied. Increased ease of handling of LC-MS/MS systems and automated/streamlined data analysis pipelines together with the accompanying increased usage of LC-MS/MS approaches will ensure that in the coming years MS-based proteomic approaches will continue to play a vital part in skin disease research. They will facilitate the elucidation of molecular disease mechanisms and, ultimately, identification of new druggable targets.

Laminin 332 in cancer: When the extracellular matrix turns signals from cell anchorage to cell movement

Laminin 332 is crucial in the biology of epithelia. This large extracellular matrix protein consists of the heterotrimeric assembly of three subunits - α3, β3, and γ2 - and its multifunctionality relies on a number of extracellular proteolytic processing events. Laminin 332 is central to normal epithelium homeostasis by sustaining cell adhesion, polarity, proliferation, and differentiation. It also supports a major function in epithelial tissue formation, repair, and regeneration by buttressing cell migration and survival and basement membrane assembly. Interest in this protein increased after the discovery that its expression is perturbed in tumor cells, cancer-associated fibroblasts, and the tumor microenvironment. This review summarizes current knowledge regarding the established involvement of the laminin 332 γ2 chain in tumor invasiveness and discusses the role of its α3 and β3 subunits.

The "other" 15-40%: The Role of Non-Collagenous Extracellular Matrix Proteins and Minor Collagens in Tendon

Extracellular matrix (ECM) determines the physiological function of all tissues, including musculoskeletal tissues. In tendon, ECM provides overall tissue architecture, which is tailored to match the biomechanical requirements of their physiological function, that is, force transmission from muscle to bone. Tendon ECM also constitutes the microenvironment that allows tendon-resident cells to maintain their phenotype and that transmits biomechanical forces from the macro-level to the micro-level. The structure and function of adult tendons is largely determined by the hierarchical organization of collagen type I fibrils. However, non-collagenous ECM proteins such as small leucine-rich proteoglycans (SLRPs), ADAMTS proteases, and cross-linking enzymes play critical roles in collagen fibrillogenesis and guide the hierarchical bundling of collagen fibrils into tendon fascicles. Other non-collagenous ECM proteins such as the less abundant collagens, fibrillins, or elastin, contribute to tendon formation or determine some of their biomechanical properties. The interfascicular matrix or endotenon and the outer layer of tendons, the epi- and paratenon, includes collagens and non-collagenous ECM proteins, but their function is less well understood. The ECM proteins in the epi- and paratenon may provide the appropriate microenvironment to maintain the identity of distinct tendon cell populations that are thought to play a role during repair processes after injury. The aim of this review is to provide an overview of the role of non-collagenous ECM proteins and less abundant collagens in tendon development and homeostasis. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:23-35, 2020.

Generation of rabbit polyclonal human and murine collagen VII monospecific antibodies: A useful tool for dystrophic epidermolysis bullosa therapy studies

High conservation of extracellular matrix proteins often makes the generation of potent species-specific antibodies challenging. For collagen VII there is a particular preclinical interest in the ability to discriminate between human and murine collagen VII. Deficiency of collagen VII causes dystrophic epidermolysis bullosa (DEB) – a genetic skin blistering disease, which in its most severe forms is highly debilitating. Advances in gene and cell therapy approaches have made curative therapies for genetic diseases a realistic possibility. DEB is one disorder for which substantial progress has been made toward curative therapies and improved management of the disease. However, to increase their efficacy further preclinical studies are needed. The early neonatal lethality of complete collagen VII deficient mice, have led researches to resort to using models maintaining residual collagen VII expression or grafting of DEB model skin on wild-type mice for preclinical therapy studies. These approaches are challenged by collagen VII expression by the murine host. Thus, the ability to selectively visualize human and murine collagen VII would be a substantial advantage. Here, we describe a novel resource toward this end. By immunization with homologous peptides we generated rabbit polyclonal antibodies that recognize either human or murine collagen VII. Testing on additional species, including rat, sheep, dog, and pig, combined sequence alignment and peptide competition binding assays enabled identification of the major antisera recognizing epitopes. The species-specificity was maintained after denaturation and the antibodies allowed us to simultaneously, specifically visualize human and murine collagen VII in situ.

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High sequence conservation of murine and human collagen VII makes development of species-specific antibodies challenging.

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Divergence in the immune epitope of a conserved peptide allowed for generation of species-specific collagen VII antibodies.

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The antibodies allow strong, simultaneous visualization of human and murine collagen VII in immunocompetent hosts.

Fibrillin microfibrils and proteases, key integrators of fibrotic pathways

Supramolecular networks composed of multi-domain ECM proteins represent intricate cellular microenvironments which are required to balance tissue homeostasis and direct remodeling. Structural deficiency in ECM proteins results in imbalances in ECM-cell communication resulting often times in fibrotic reactions. To understand how individual components of the ECM integrate communication with the cell surface by presenting growth factors or providing fine-tuned biomechanical properties is mandatory for gaining a better understanding of disease mechanisms in the quest for new therapeutic approaches. Here we provide an overview about what we can learn from inherited connective tissue disorders caused primarily by mutations in fibrillin-1 and binding partners as well as by altered ECM processing leading to defined structural changes and similar functional knock-in mouse models. We will utilize this knowledge to propose new molecular hypotheses which should be tested in future studies.

Platelet-Rich Plasma, Adipose Tissue, and Scar Modulation

Level of Evidence: 4.

Inhibitors of BMP-1/tolloid-like proteinases: efficacy, selectivity and cellular toxicity

BMP‐1/tolloid‐like proteinases belong to the astacin family of human metalloproteinases, together with meprins and ovastacin. They represent promising targets to treat or prevent a wide range of diseases such as fibrotic disorders or cancer. However, the study of their pathophysiological roles is still impaired by the lack of well‐characterized inhibitors and the questions that remain regarding their selectivity and in vivo efficiency. As a first step towards the identification of suitable tools to be used in functional studies, we have undertaken a systematic comparison of seven molecules known to affect the proteolytic activity of human astacins including three hydroxamates (FG‐2575, UK383,367, S33A), the protein sizzled, a new phosphinic inhibitor (RXP‐1001) and broad‐spectrum protease inhibitors (GM6001, actinonin). Their efficacy in vitro, their cellular toxicity and efficacy in cell cultures were thoroughly characterized. We found that these molecules display very different potency and selectivity profiles, with hydroxamate FG‐2575 and the protein sizzled being very powerful and selective inhibitors of BMP‐1, whereas phosphinic peptide RXP‐1001 behaves as a broad‐spectrum inhibitor of astacins. Their use should therefore be carefully considered in agreement with the aim of the study to avoid result misinterpretation.

Epidermolysis bullosa: Molecular pathology of connective tissue components in the cutaneous basement membrane zone

Epidermolysis bullosa (EB), a group of heritable skin fragility disorders, is characterized by blistering, erosions and chronic ulcers in the skin and mucous membranes. In some forms, the blistering phenotype is associated with extensive mutilating scarring and development of aggressive squamous cell carcinomas. The skin findings can be associated with extracutaneous manifestations in the ocular as well as gastrointestinal and vesico-urinary tracts. The phenotypic heterogeneity reflects the presence of mutations in as many as 20 different genes expressed in the cutaneous basement membrane zone, and the types and combinations of the mutations and their consequences at the mRNA and protein levels contribute to the spectrum of severity encountered in different subtypes of EB. This overview highlights the molecular genetics of EB based on mutations in the genes encoding type VII and XVII collagens as well as laminin-332. The mutations identified in these protein components of the extracellular matrix attest to their critical importance in providing stability to the cutaneous basement membrane zone, with implications for heritable and acquired diseases.

Matrix modeling and remodeling: A biological interplay regulating tissue homeostasis and diseases

The overall structure and architecture of the extracellular matrix undergo dramatic alterations in composition, form, and functionality over time. The stochasticity begins during development, essential for maintaining organismal homeostasis and is heavily implicated in many pathobiological states including fibrosis and cancer. Modeling and remodeling of the matrix is driven by the local cellular milieu and secreted and cell-associated components in a framework of dynamic reciprocity. This collection of expertly-written reviews aims to relay state-of-the-art information concerning the mechanisms of matrix modeling and remodeling in physiological development and disease.

Matrix molecules and skin biology

An extracellular matrix (ECM) is a prerequisite for multicellular life. It is adapted to tissues and constantly undergoes changes to preserve microenvironmental homeostasis. The ECM acts as a structural scaffold that establishes tissue architecture and provides tensile strength. It has cell-instructive functions by serving as a reservoir and presenter of soluble agents, being directly signaling, integrating transmission of mechanical and biological cues, or serving as a co-factor potentiating signaling. The skin contains a highly developed, mechanically tough, but yet flexible ECM. The tissue-specific features of this ECM are largely attributed by minor ECM components. A large number of genetic and acquired ECM diseases with skin manifestations, provide an illustrative testament to the importance of correct assembly of the ECM for dermal homeostasis. Here, we will present the composition and features of the skin ECM during homeostasis and regeneration. We will discuss genetic and acquired ECM diseases affecting skin, and provide a short outlook to therapeutic strategies for them.

Cardiovascular function and structure are preserved despite induced ablation of BMP1-related proteinases

Introduction

Bone morphogenetic protein 1 (BMP1) is part of an extracellular metalloproteinase family that biosynthetically processes procollagen molecules. BMP1- and tolloid-like (TLL1) proteinases mediate the cleavage of carboxyl peptides from procollagen molecules, which is a crucial step in fibrillar collagen synthesis. Ablating the genes that encode BMP1-related proteinases (Bmp1 and Tll1) post-natally results in brittle bones, periodontal defects, and thin skin in conditional knockout (BT^KO) mice. Despite the importance of collagen to cardiovascular tissues and the adverse effects of Bmp1 and Tll1 ablation in other tissues, the impact of Bmp1 and Tll1 ablation on cardiovascular performance is unknown. Here, we investigated the role of Bmp1- and Tll1-ablation in cardiovascular tissues by examining ventricular and vascular structure and function in BT^KO mice.

Methods

Ventricular and vascular structure and function were comprehensively quantified in BT^KO mice (n=9) and in age- and sex-matched controls (n=9). Echocardiography, cardiac catheterization, and biaxial ex vivo arterial mechanical testing were performed to assess tissue function, and histological staining was used to measure collagen protein content.

Results

Bmp1- and Tll1-ablation resulted in maintained hemodynamics and cardiovascular function, preserved biaxial arterial compliance, and comparable ventricular and vascular collagen protein content.

Conclusions

Maintained ventricular and vascular structure and function despite post-natal ablation of Bmp1 and Tll1 suggests that there is an as-yet unidentified compensatory mechanism in cardiovascular tissues. In addition, these findings suggest that proteinases derived from Bmp1 and Tll1 post-natally have less of an impact on cardiovascular tissues compared to skeletal, periodontal, and dermal tissues.

Opposing Roles of Epidermal Integrins α3β1 and α9β1 in Regulation of mTLD/BMP-1-Mediated Laminin-γ2 Processing during Wound Healing

Proteolytic processing of the laminin-γ2 chain is a hallmark of basement membrane maturation in the skin. Integrin α3β1, a major receptor for epidermal adhesion to laminin-332, is critical for proper basement membrane organization during skin development and wound healing. Previously, we identified a role for α3β1 in promoting the processing of laminin-γ2 in cultured keratinocytes in vitro and in wound epidermis in vivo. In this study we identify the Bmp1 gene, which encodes variants of the mTLD/BMP-1 metalloproteases, as a critical regulator of α3β1-dependent laminin-γ2 processing, thereby expanding the role of this integrin in controlling the secretion by the epidermis of factors that modulate the tissue microenvironment. Because our previous studies identified another epidermal integrin, α9β1, as a suppressive regulator of α3β1-dependent wound angiogenesis, we investigated whether α9β1 has a similar cross-suppressive effect on the ability of α3β1 to promote basement membrane organization. Here, we show that, rather than a cross-suppressive role, α9β1 has an opposing role in basement membrane assembly/maturation through reduced laminin-γ2 processing via mTLD/BMP-1. Although α3β1 promotes this process during wound healing, α9β1 has an inhibitory role, suggesting that regulation of basement membrane assembly requires a complex interplay between these distinct epidermal integrins.

Extracellular matrix contribution to skin wound re-epithelialization

The ability of skin to act as a barrier is primarily determined by cells that maintain the continuity and integrity of skin and restore it after injury. Cutaneous wound healing in adult mammals is a complex multi-step process that involves overlapping stages of blood clot formation, inflammation, re-epithelialization, granulation tissue formation, neovascularization, and remodeling. Under favorable conditions, epidermal regeneration begins within hours after injury and takes several days until the epithelial surface is intact due to reorganization of the basement membrane. Regeneration relies on numerous signaling cues and on multiple cellular processes that take place both within the epidermis and in other participating tissues. A variety of modulators are involved, including growth factors, cytokines, matrix metalloproteinases, cellular receptors, and extracellular matrix components. Here we focus on the involvement of the extracellular matrix proteins that impact epidermal regeneration during wound healing.

Decorin is a devouring proteoglycan: Remodeling of intracellular catabolism via autophagy and mitophagy

Autophagy, a fundamental and evolutionarily-conserved eukaryotic pathway, coordinates a complex balancing act for achieving both nutrient and energetic requirements for proper cellular function and homeostasis. We have discovered that soluble proteoglycans evoke autophagy in endothelial cells and mitophagy in breast carcinoma cells by directly interacting with receptor tyrosine kinases, including VEGF receptor 2 and Met. Under these circumstances, autophagic regulation is considered "non-canonical" and is epitomized by the bioactivity of the small leucine-rich proteoglycan, decorin. Soluble matrix-derived cues being transduced downstream of receptor engagement converge upon a newly-discovered nexus of autophagic machinery consisting of Peg3 for endothelial cell autophagy and mitostatin for tumor cell mitophagy. In this thematic mini-review, we will provide an overview of decorin-mediated autophagy and mitophagy and propose that regulating intracellular catabolism is the underlying molecular basis for the versatility of decorin as a potent oncosuppressive agent.

Procollagen C-proteinase enhancer 1 (PCPE-1) functions as an anti-angiogenic factor and enhances epithelial recovery in injured cornea

Procollagen C-proteinase enhancer 1 (PCPE-1) has been characterized as a protein capable of enhancing the activity of bone morphogenetic protein 1/tolloid-like proteinases in the biosynthetic processing of C-propeptides from procollagens I-III. This processing step is thought necessary to the formation of collagen I-III monomers capable of forming fibrils. Thus, PCPE-1 is predicted to play an important role in scarring, as scar tissue is predominantly composed of fibrillar collagen. Corneal scarring is of great clinical importance, as it leads to loss of visual acuity and, in severe cases, blindness. Here, we investigate a possible role for PCPE-1 in corneal scarring. Although differences in corneal opacity associated with scarring following injury of Pcolce ^-/- and wild-type (WT) mice using full-thickness excision or alkali burn models of corneal injury were not grossly apparent, differences in procollagen I processing levels between Pcolce ^-/- and WT primary corneal keratocytes were consistent with a role for PCPE-1 in corneal collagen deposition. An unexpected finding was that neoangiogenesis, which follows alkali burn cornea injury, was strikingly increased in Pcolce ^-/- cornea, compared to WT. A series of aortic ring assays confirmed the anti-angiogenic effects of PCPE-1. Another unexpected finding was of abnormalities of epithelial basement membrane and of re-epithelialization following Pcolce ^-/- corneal injury. Thus, PCPE-1 appears to be of importance as an anti-angiogenic factor and in re-epithelialization following injury in cornea and perhaps in other tissues as well.

Identification of a myofibroblast-specific expression signature in skin wounds

After skin injury fibroblasts migrate into the wound and transform into contractile, extracellular matrix-producing myofibroblasts to promote skin repair. Persistent activation of myofibroblasts can cause excessive fibrotic reactions, but the underlying mechanisms are not fully understood. We used SMA-GFP transgenic mice to study myofibroblast recruitment and activation in skin wounds. Myofibroblasts were initially recruited to wounds three days post injury, their number reached a maximum after seven days and subsequently declined. Expression profiling showed that 1749 genes were differentially expressed in sorted myofibroblasts from wounds seven days post injury. Most of these genes were linked with the extracellular region and cell periphery including genes encoding for extracellular matrix proteins. A unique panel of core matrisome and matrisome-associated genes was differentially expressed in myofibroblasts and several genes not yet known to be linked to myofibroblast-mediated wound healing were found (e.g. Col24a1, Podnl1, Bvcan, Tinagl1, Thbs3, Adamts16, Adamts19, Cxcl's, Ccl's). In addition, a complex network of G protein-coupled signaling events was regulated in myofibroblasts (e.g. Adcy1, Plbc4, Gnas). Hence, this first characterization of a myofibroblast-specific expression profile at the peak of in situ granulation tissue formation provides important insights into novel target genes that may control excessive ECM deposition during fibrotic reactions.

Current Therapeutic Approach to Hypertrophic Scars

Abnormal scarring and its accompanying esthetic, functional, and psychological sequelae still pose significant challe nges. To date, there is no satisfactory prevention or treatment option for hypertrophic scars (HSs), which is mostly due to not completely comprehending the mechanisms underlying their formation. That is why the apprehension of regular and controlled physiological processes of scar formation is of utmost importance when facing hypertrophic scarring, its pathophysiology, prevention, and therapeutic approach. When treating HSs and choosing the best treatment and prevention modality, physicians can choose from a plethora of therapeutic options and many commercially available products, among which currently there is no efficient option that can successfully overcome impaired skin healing. This article reviews current therapeutic approach and emerging therapeutic strategies for the management of HSs, which should be individualized, based on an evaluation of the scar itself, patients’ expectations, and practical, evidence-based guidelines. Clinicians are encouraged to combine various prevention and treatment modalities where combination therapy that includes steroid injections, 5-fluorouracil, and pulsed-dye laser seems to be the most effective. On the other hand, the current therapeutic options are usually empirical and their results are unreliable and unpredictable. Therefore, there is an unmet need for an effective, targeted therapy and prevention, which would be based on an action or a modulation of a particular factor with clarified mechanism of action that has a beneficial effect on wound healing. As the extracellular matrix has a crucial role in cellular and extracellular events that lead to pathological scarring, targeting its components mostly by regulating bone morphogenetic proteins may throw up new therapeutic approach for reduction or prevention of HSs with functionally and cosmetically acceptable outcome.

BMP1 and TLL1 Are Required for Maintaining Periodontal Homeostasis

Mutations in bone morphogenetic protein 1 (BMP1) in humans or deletion of BMP1 and related protease tolloid like 1 (TLL1) in mice lead to osteogenesis imperfecta (OI). Here, we show progressive periodontal defects in mice in which both BMP1 and TLL1 have been conditionally ablated, including malformed periodontal ligament (PDL) (recently shown to play key roles in normal alveolar bone formation), significant loss in alveolar bone mass ( P < 0.01), and a sharp reduction in cellular cementum. Molecular mechanism studies revealed a dramatic increase in the uncleaved precursor of type I collagen (procollagen I) and a reduction in dentin matrix protein 1 (DMP1), which is partially responsible for defects in extracellular matrix (ECM) formation and mineralization. We also showed a marked increase in the expression of matrix metallopeptidase 13 (MMP13) and tartrate-resistant acid phosphatase (TRAP), leading to an acceleration in periodontal breakdown. Finally, we demonstrated that systemic application of antibiotics significantly improved the alveolar bone and PDL damage of the knockdown phenotype, which are thus shown to be partially secondary to pathogen-induced inflammation. Together, identification of the novel roles of BMP1 and TLL1 in maintaining homeostasis of periodontal formation, partly via biosynthetic processing of procollagen I and DMP1, provides novel insights into key contributions of the extracellular matrix environment to periodontal homeostasis and contributes toward understanding of the pathology of periodontitis.

Proteoglycan neofunctions: regulation of inflammation and autophagy in cancer biology

Inflammation and autophagy have emerged as prominent issues in the context of proteoglycan signaling. In particular, two small, leucine-rich proteoglycans, biglycan and decorin, play pivotal roles in the regulation of these vital cellular pathways and, as such, are intrinsically involved in cancer initiation and progression. In this minireview, we will address novel functions of biglycan and decorin in inflammation and autophagy, and analyze new emerging signaling events triggered by these proteoglycans, which directly or indirectly modulate these processes. We will critically discuss the dual role of proteoglycan-driven inflammation and autophagy in tumor biology, and delineate the potential mechanisms through which soluble extracellular matrix constituents affect the microenvironment associated with inflammatory and neoplastic diseases.

The nature and biology of basement membranes

Basement membranes are delicate, nanoscale and pliable sheets of extracellular matrices that often act as linings or partitions in organisms. Previously considered as passive scaffolds segregating polarized cells, such as epithelial or endothelial cells, from the underlying mesenchyme, basement membranes have now reached the center stage of biology. They play a multitude of roles from blood filtration to muscle homeostasis, from storing growth factors and cytokines to controlling angiogenesis and tumor growth, from maintaining skin integrity and neuromuscular structure to affecting adipogenesis and fibrosis. Here, we will address developmental, structural and biochemical aspects of basement membranes and discuss some of the pathogenetic mechanisms causing diseases linked to abnormal basement membranes.